website: add support for JS/TS unit testing

Change-Id: I8bb35b7183c07c44c5e5da8dc2f2c15cc38ea64b
Reviewed-on: https://go-review.googlesource.com/c/website/+/377734
Run-TryBot: Jamal Carvalho <jamal@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alex Rakoczy <alex@golang.org>
Trust: Jamal Carvalho <jamalcarvalho@google.com>
diff --git a/.eslintrc.yaml b/.eslintrc.yaml
index 09d6a43..a3c2d0a 100644
--- a/.eslintrc.yaml
+++ b/.eslintrc.yaml
@@ -1,7 +1,7 @@
 root: true
 extends: google
 parserOptions:
-  ecmaVersion: 6
+  ecmaVersion: 2018
 rules:
   require-jsdoc: 'off'
   indent: 'off'